1. Field of the Invention
The present invention relates to transmitters applicable to touch sensitive panels, and more particularly, to a transmitter that is capable of replacing one or more frequencies when under interference.
2. Description of the Prior Art
Touch sensitive panels or screens are important human-machine interfaces, especially for consumer electronic products like portable phones, tablet PCs, or Personal Digital Assistances (PDAs). Touch sensitive screens are one of the main input/output (I/O) devices. As capacitive touch sensitive screens, especially those of projected capacitive types, are highly sensitive to finger touches, it has become one of the main design choices for touch sensitive panels/screens on the market.
Touching the screen with the tip of a finger will inevitably block part of the screen, and the user will not be able to visually confirm a point that is being detected by the touch sensitive. In addition, one cannot have as accurate control as using a pen (or stylus) when using their finger tip(s) to write. Therefore, in addition to using finger tips for touch control, users may also wish to use a stylus for input to the screen.
Generally, the area on a touch sensitive screen touched by the tip of a stylus is much smaller than that touched by the fingertips. For capacitive touch sensitive screens, it has been a challenge to detect the capacitive changes caused by a stylus. In particular, in many professional graphics or typesetting application environments, a lot of functional buttons needs to be added in the design process of the stylus. In view of this demand, the touch sensitive screen not only needs to detect the tiny tip of the stylus, but also needs to determine whether these buttons are being pressed.
Furthermore, there are many electromagnetic interferences in the modern environment in which we live in. In addition to achieving the objectives above, the screen needs to be able to avoid these electromagnetic interferences when trying to detect the stylus. In summary, there is a need on the market for a stylus that supports multiple function inputs when subjected to electromagnetic interferences, thereby allowing a touch sensitive screen to detect the stylus while detecting the statues of the functional buttons.